Senators warned Tuesday that the future of U.S. offshore drilling is in doubt unless oil industry executives stop trading blame for the Gulf oil spill and take steps to prevent such an accident from happening again.

In heated testimony on Capitol Hill, executives from the companies that owned and operated the Deepwater Horizon oil rig pointed fingers at each other for its April 20 explosion off Louisiana's coast. Efforts to cap the well, which the government estimates is leaking at least 5,000 barrels of oil per day, have been complicated by the fact that officials still do not fully understand what caused the disaster.

President Obama has said new offshore drilling projects are on hold until the cause of the leak can be investigated.

"This incident will have an impact on developing our energy policy for this country," Sen. Lisa Murkowski, the ranking Republican on the energy committee and a proponent of drilling, told the executives. "We are all in this together."

Lamar McKay, chairman of energy company BP America, said BP is responsible for cleaning up damages from the leak because it was operating the rig. However, he said the failure of a safety seal was the responsibility of Transocean, the rig's owner.

Salazar also announced plans to divide the government's Minerals Management Service into two separate entities — a move that will help prevent conflicts of interest by separating safety regulators from officials who collect oil royalties.

Environmental Protection Agency chief Lisa Jackson said additional tests will be held to determine whether vapors from the spill, or the chemicals being used to stop it from spreading, pose a hazard to rescue workers or Gulf residents.

"So far we haven't seen anything that causes us to believe there's a potential to impact human health," Jackson said in a telephone interview from Louisiana. "But we're going to do some additional testing … and keep a close eye on it."

Three weeks after the spill, winds and currents have kept most of the thickest oil from shore. "Time has given us a leg up," Jackson said. "But we have to anticipate our plans won't be foolproof."

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